Bitmap.LockBits是否将位图“固定”到内存中？-DoesBitmap.LockBits“pin”abitmapintomemory?

8  

GCHandle.Alloc is a more generic method, that allows you to allocate a handle to any managed object and pin it in memory (or not). Pinning memory prevents GC from moving it around, which is especially useful when you have to pass some data, for example an array, to a unmanaged code.

GCHandle.Alloc是一种更通用的方法,允许您为任何托管对象分配句柄并将其固定在内存中(或不固定)。固定内存会阻止GC移动它,这在您必须将某些数据(例如数组)传递给非托管代码时尤其有用。

GCHandle.Alloc will not help you access bitmap's data in any way, because pinning this object will just prevent the managed object from moving around (the Bitmap object) (and being garbage collected).

GCHandle.Alloc不会以任何方式帮助您访问位图的数据,因为固定此对象只会阻止托管对象移动(Bitmap对象)(并进行垃圾回收)。

Bitmap however is a wrapper around native GDI+'s BITMAP structure. It doesn't keep data in any managed array that you would have to pin, it just managed a native handle to GDI+ bitmap object. Because of that Bitmap.LockBits is a way of telling this bitmap that you are interested in accessing it's memory, and it's just a wrapper around GdipBitmapLockBits function. So your need of calling it has more to do with the fact that you are working with GDI+ bitmaps than with the fact, that you're working in managed environment with GC.

然而,Bitmap是本机GDI +的BITMAP结构的包装器。它不会将数据保存在您必须固定的任何托管数组中,它只是管理了GDI +位图对象的本机句柄。因为Bitmap.LockBits是一种告诉这个位图的方式,你有兴趣访问它的内存,它只是GdipBitmapLockBits函数的包装器。因此,您需要调用它更多地与您使用GDI +位图这一事实有关,而不是与您在使用GC的托管环境中工作的事实有关。

Once you have used LockBits you should be able to access it's memory using pointers through BitmapData.Scan0 - it's an address of first byte of data. You should not have problems as long, as you do not access memory behind BitmapData.Scan0 + Height * Stride.

一旦你使用了LockBits,你应该能够通过BitmapData.Scan0使用指针访问它的内存 - 它是数据第一个字节的地址。你应该没有问题,因为你没有访问BitmapData.Scan0 + Height * Stride后面的内存。

And rememberto UnlockBits when you are done.

当你完成时,记得UnlockBits。

1  

In your case an attempted to access invalid memory error is most probably caused by invalid memory allocation which you are doing in the unsafe part of code, e.g allocated array is smaller than number of pixels you are trying to put in that.

在您的情况下,尝试访问无效内存错误很可能是由于您在代码的不安全部分进行的无效内存分配造成的,例如,分配的数组小于您尝试放入的像素数。

There is also no need to think about pinning the objects unless your image data is less than 85000 Bytes as only objects less than 85K will be moved in memory.

除非您的图像数据小于85000字节,否则也无需考虑固定对象,因为只有小于85K的对象将在内存中移动。

Another story would be if you pass the object to unmanaged code, for example in the c++ library for faster processing. In this case your exception is very possible if the passed image gets out of scope and will be garbage collected. In this case you can use GCHandle.Alloc(imageArray,GCHandleType.Pinned); and than call Free if you do not need it any longer.

另一个故事是,如果您将对象传递给非托管代码,例如在c ++库中以便更快地处理。在这种情况下,如果传递的图像超出范围并且将被垃圾收集,则很可能发生异常。在这种情况下,您可以使用GCHandle.Alloc(imageArray,GCHandleType.Pinned);如果您不再需要它,请致电免费。